670 GEOFFREY LAPAGE 



down, SO that the drop hung in a sealed chamber. A small 

 drop of water was placed on the bottom of the chamber before 

 it was closed, as an additional precaution against evaporation. 

 These preparations were similar to those used for the study of 

 Helkestimastix (Woodcock and Lapage, 31) and in them the 

 amoebae could bo observed for several days. It was found that, 

 after a day or two, all the organisms in the drops, and especially 

 Cihata such as P a r a m o e c i u m b u r s a r i a , became very 

 sluggish ; but they could be readily re^dved by lifting the 

 cover-glass for a few minutes and replacing it again. The 

 renewal of the air in the chamber, effected in this way, had 

 a remarkably invigorating effect upon the organisms, the 

 Paramoecium bursaria, for example, immediately 

 resuming their normal lively activity. The method had the 

 additional advantage that the organisms under observation 

 could be fixed at any desired moment, by simply removing 

 the cover-glass, spreading out the drop upon it, after removing 

 the adherent vaseline, and then dropping the film on to the 

 surface of a dish of fixative. 



Permanent preparations were constantly made in this manner. 

 In addition amoebae were daily taken from the cultures and 

 fixed upon albumenized slides, the culture fluid being spread 

 out in a thin film before the fixative was added. 



The fixative used w^as that introduced by Dr. H. M. Wood- 

 cock and was made up of two parts of a saturated solution 

 of corrosive sublimate in water to one part of absolute alcohol 

 with glacial acetic acid in the proportion of 5 per cent. Most of 

 the slides were stained by Dobell's alcoholic modification of 

 Heidenhain's iron haematoxylin method (Dobell, 8). This 

 method, though in some respects inferior to the watery iron 

 haematoxylin method, gave very good results. It has the 

 double advantage over the watery method of being quicker 

 and of avoiding the treatment of the preparation with water 

 or the lower grades of alcohol, in which many organisms, 

 unless previously hardened overnight in 70 per cent, or 90 per 

 cent, alcohol, are frequently washed ofi". It is undoubtedly 

 a very useful and reliable method for staining all kinds of 



